The present invention relates to a process for the manufacture of ureas and, more particularly, to a process for the manufacture of ureas by reaction of a nitrogenous compound having at least one hydrogen atom attached to the nitrogen or water with carbon monoxide and a nitrogenous compound in which the nitrogen is directly attached to a single carbon atom and also is attached through a double bond to an oxygen or another nitrogen under elevated temperatures and pressure conditions in a basic solution and in the presence of a sulfur or selenium catalyst.
Urea and substituted ureas are important intermediates in the preparation of various products, particularly agricultural chemicals useful in soil treatment, as fungicides, insecticides, and germicides, in weed control and other uses. For example 3-(3,4-dichlorophenyl)-1,1-dimethylurea is a preemergence weed control product; 1,1-dimethyl-3-phenylurea is an excellent herbicide; and 3-(p-chlorophenyl)-1,1-dimethylurea is a non-selective weed control product. Thus any method which can be used to produce these and similar ureas is a valuable and useful process.
It is well known in the art to produce ureas by the reaction of an amine compound with an isocyanate or alternatively by the reaction of an amine with phosgene; the reaction chosen is dependent upon the nature of the desired urea. Such processes suffer from a number of disadvantages among which are the necessity for handling toxic and highly reactive compounds, the expense of the starting compounds and the necessity of working in expensive corrosion resistant apparatus resistant to by-product hydrogen chloride generated in the phosgene reaction. Other procedures are available; for example in U.S. Pat. No. 2,877,268 there is described a process for preparing ureas by an apparently noncatalytic reaction of amines with carbonyl sulfide, while British Pat. No. 1,275,702 describes a catalytic process for converting amines to ureas using selenium, carbon monoxide and oxygen. It should be noted that in each of the processes it is an amine that is converted to a urea.
The instant invention is a simple one-step process for the preparation of ureas which eliminates the need for an isocyanate, phosgene, and in one embodiment water is used instead of an amine. Thus it is possible to start with cheaper and more readily available nitrogen-containing organic compounds.